Image sensors have become ubiquitous. They are widely used in digital still cameras, cellular phones, security cameras, as well as, medical, automobile, and other applications. The technology used to manufacture image sensors, and in particular, complementary metal-oxide-semiconductor (“CMOS”) image sensors, has continued to advance at great pace. For example, the demands of higher resolution and lower power consumption have encouraged the further miniaturization and integration of these image sensors.
Some conventional image sensors incorporate in-pixel memory. For example, U.S. Pat. No. 8,445,828, which is incorporated herein by reference, describes a high dynamic range CMOS image sensor that incorporates in-pixel memory for varying integration periods. That is, integration periods are determined, in part, by signals stored in the in-pixel memory from previous integration periods. Each pixel includes a memory latch circuit that stores integration period information relating to that pixel. Each of these memory elements can be accessed individually. However, some of the circuit elements incorporated in the in-pixel memory may be sensitive to light-induced leakage.